Modern liquid cooled internal combustion engines incorporate sealed radiators coupled to the engines to dissipate heat generated by the engine. As coolant fluid passes through the radiator heat is given off to the environment. Typically, the coolant system will include a separate coolant container for filling the radiator and capturing any overflow of fluid due to thermal expansion. These coolant containers are known in the art as expansion bottles or surge tanks. Coolant container caps are designed to engage with a neck portion of the coolant container and perform a number of specific functions. The primary function is to provide a seal for the fluid within the coolant system.
Another typical function of the coolant container cap is to maintain a predetermined pressure within the radiator/coolant container assembly. This is usually accomplished by a valve and sealing assembly located within the cap. During normal operations of the engine the valve and sealing assembly is closed to prevent the escape of fluid from the coolant system. A certain amount of pressure build up within the radiator and coolant container is desirable for efficient operation of the radiator. Hence, the cap must maintain an adequate seal between the coolant system and the atmosphere.
However, when the pressure within the coolant system reaches a predetermined super-atmospheric level, a pressure plate valve of the valve and sealing assembly automatically opens to release the pressure within the coolant container and prevent excess pressure build up. When the pressure within the tank drops to a predetermined sub-atmospheric level, a vacuum plate valve of the valve and sealing assembly opens to equalize the pressure in the coolant system. The valve and sealing assembly is required in order to prevent dangerous build up of pressure within the radiator.
As discussed above, a certain amount of fluid pressure within the coolant system is required for efficient operation of the engine. When the engine is not operating and the engine and radiator have cooled to an ambient temperature the pressure within the radiator and coolant container becomes negligible. However, if a user attempts to remove the cap while the coolant system is still pressurized then there could be significant injury to the users face and/or body.
The prior art has contemplated a solution to this potentially dangerous problem. U.S. Pat. No. 4,767,390 contemplates actuating a valve and sealing assembly moments before a cap is removed from a pressurized tank. Therefore, the pressure will be released via the valve and sealing assembly and directed away from a user. This solution however has a number of deficiencies. One such deficiency is the complexity of the cap which utilizes a type of plunger for actuating the valve and sealing assembly as the cap is rotated. Another deficiency is the frequent use of the valve and sealing assembly, i.e. each time the cap is removed. This frequent use can reduce the effective operating life of the cap.